The urbanization of cities and the density of land use have led to the creation of vast impervious surfaces such as streets, sidewalks, buildings and parking lots. This situation means that rainwater and runoff no longer penetrate the soil naturally to return to the water table, which irrigates the land and feeds the grass, shrubs and trees.

Centropolis understands this situation and has developed a portion of its parking lot, located in the area of La Cordée and Cinémas Cineplex, by respecting the water discharges to the storm sewer system that the municipal system can support, but also by creating an open-air and naturalized water retention basin. This retention basin, as its name indicates, allows for the temporary containment of a significant volume of water during episodes of intense rainfall. The water is held there until the municipal sewer system is able to handle it. This retention pond is different from conventional retention structures, which are built in oversized pipes or underground tanks, or on the surface of the parking lot. In fact, it is combined with an infiltration and purification garden. The basin accommodates both a portion of the rainfall that falls naturally on the site and the large volumes generated by major rainfall events. The water that passes through the basin has the opportunity to be captured by the perennial plants and shrubs before reaching the infiltration garden located at the bottom.

In this way, the water from the rainfall is purified by the plants and micro-organisms in the soil as it infiltrates deeply and then recharges the water table. An important part of the water is also absorbed by the plants, which release it into the atmosphere by evapotranspiration.

The action of Centropolis is therefore not trivial. It allows water to return more naturally to the soil and to the air. Moreover, this water is of better quality when it is returned to the municipal network, thus reducing the efforts of the entire community. By dedicating a portion of its property to this water retention, purification and infiltration basin, Centropolis is creating a high quality green space that increases biodiversity and biomass, combats heat islands and provides a place for birds and small local wildlife to live, protect and feed.